Injured opener Colin Munro's fitness is improving. He is expected to tour when the squad is announced later today.
Hesson lamented a series of dropped catches which cost several runs across the Pakistan innings.
"[Fielding] is certainly something we pride ourselves on, by being clinical in how we operate.
"Our ground fielding was good at times but, when you shell catches, it has an effect."
Hesson paid tribute to the skills of 19-year-old leg spinner Shadab Khan, who earned man-of-the-match with his two for 19 from four overs. Both his wickets – Anaru Kitchen and Martin Guptill - came in the 13th over.
"We just kept getting behind the run rate, but Shadab's spell turned the game a bit, especially the fact he bowled four on the bounce.
"In hindsight, maybe you want to suck it up, but at the time the run rate's going up and you make a play. He bowled wide of off stump and spun it nicely from there, which took away a lot scoring options.
"We were put under pressure for large proportions of the innings and chased the game a bit."
Arthur said Shadab's second wicket, the dismissal of Martin Guptill for 59 off 43 balls, was key to the result.
"We were sitting in the dressing room going 'this is a crucial ball, this will determine the way the match goes'. It was six or out.
"Shadab knows the game, he's smart in the way he analyses it and he knew that was a pinnacle point. He proved his class throughout the series. Yes, he's young, but he's become our go-to guy.
"I'd also mention of [man-of-the series] Mohammad Amir. When games are on the line he's turned up wanting the ball, that's testimony to his character. I've always said he's a big match player."
Arthur spoke candidly to media in Wellington when they lost the ODI series 5-0.
He felt at his "wit's end" then, but vindicated now.
"We knew we had underperformed. I can't praise the guys more in their work ethic and character to turn it around in the T20s.
"If there's one thing we've learned it's that when we leave the guys alone for five weeks it takes us a long time to get back to the required skills. I'm just pleased the New Zealand public got to see the real Pakistan, because we were clinical in the last two games, particularly in the field. [Fielding coach] Steve Rixon is a tough taskmaster.
"The training before the Eden Park match was probably one of the most intense I've been privy to in 10 years of international cricket coaching. The way the guys went about their business was phenomenal."
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